Systems are known which are capable of synthesizing two dimensional images in response to data defining elements within a three dimensional space. The final two-dimensional result may consist of a very large number of colored pictured elements (pixels) which may be viewed on a monitor or printed onto an image carrying medium.
In interactive systems arranged to generate data representing a three-dimensional space, objects appear to move within the three-dimensional space in response to input commands. Thus, in such systems a machine is required to render a two-dimensional image from data representing a three-dimensional space repeatedly, as the position and/or orientation of objects, light sources and view position change in response to input commands. Typically, in an interactive environment, a machine is required to produce output images at a rate of between five to twenty per second.
Interactive three-dimensional graphics systems have many applications and these applications could be extended further if many users could share access to a common three-dimensional world. Thus, information could be recorded in three-dimensional space and many users, each with their own display device, could be given access to this space, allowing them to observe the data created by other users and, possibly, modify this data. Thus, an interchange of ideas could be provided by giving access to shared three-dimensional data.
In interactive graphics systems output images are usually displayed on a monitor, similar to a conventional television receiver. Thus, a processor is required to generate a video signal which is supplied to the monitor at video rate. Often data is supplied to a frame buffer at an interactive rate and image data is then read from the frame buffer at video rate, in order to generate the video signal. Typically, a look-up table is provided, allowing a selection of colors to be defined in response to selections made by the limited number of bits stored in the look-up table. The look-up table itself may define particular colors and include values representing modifications to luminance and saturation.
Techniques for the transmission of video signals are well known and, in addition to one-way television broadcasts, it is also known to provide two-way video communication, such as in video conferencing facilities or video telephones.
However, a problem with transmitting video signals is that a substantial bandwidth is required, therefore transmission costs become high. A further problem arises, when sharing access to a three-dimensional world, in that additional communication channels are required for the control of access to that world, along with processing facilities to resolve contention problems. Furthermore, although the video image includes a large amount of data, it only represents a particular view of the three-dimensional world, rendered from a particular view point. Thus, any attempt to provide multiple access to the three-dimensional data is restricted to the particular view under consideration.
It is an object of the present invention to provide an improved apparatus for displaying three-dimensional images, in which a first station and a second station have shared access.